feat(docs): source install w/ cloudsmith

[curiositycasualty]

Summary

This swaps the install instructions that previously mentioned download.konghq.com for ones that now mention package.konghq.com / https://cloudsmith.io/~kong/repos/insomnia & https://cloudsmith.io/~kong/repos/insomnia-legacy

Reason

Pulp is being deprecated.

Testing

docker run --rm -it ubuntu bash -c 'apt update -y && apt install -y curl sudo && curl -1sLf https://packages.konghq.com/public/insomnia/setup.deb.sh | sudo -E distro=ubuntu codename=focal bash && apt-cache search insomnia'

[vercel]

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Name	Status	Preview	Updated (UTC)
insomnia-docs	✅ Ready (Inspect)	Visit Preview	Feb 7, 2024 0:21am

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